1. Field of the Invention
This invention relates to an exhaust gas recirculation apparatus and system for an internal combustion engine which has an air intake system and an exhaust system. Exhaust gas is introduced to fresh air in the air intake via an exhaust-gas recirculation line and an exhaust-gas recirculation valve.
2. Description of Related Art
Exhaust gas recirculation apparatus and systems for an internal combustion engines are known. It is also known that part-load engine operation produces cooling of the exhaust gases and the recirculation valve in previous systems. During part-load operation under particular temperatures, a lacquer-like coating can form on the exhaust gas recirculation valve which could inhibit its operation.
The primary object of the invention is to design and configure the exhaust gas recirculation system so that formation of lacquer-like substances are prevented from forming on the recirculation valve or valve seat.
According to the invention, the object of preventing formation of a lacquer-like substance is achieved by arranging the exhaust gas recirculation valve so as not to be exposed to air intake flow. This tends to prevent cooling of the recirculation valve by contact with the flow of fresh air. As a result, the recirculation valve does not come into contact with crankcase oil entrained in the flow of intake air. The exhaust-gas recirculation valve may be located at any desired point between the cylinder head and exhaust-gas supply device. By separating the exhaust gas recirculation valve from crankcase ventilation oil entrained in the intake air prevents clogging of the valve caused by formation of a soot/oil mixture on the valve and valve seat.
In accordance with a preferred embodiment of the invention, the exhaust gas recirculation valve includes an actuator and the actuator in the recirculation valve is operated electromechanically. The electromechanical actuator is seated directly on the exhaust-gas recirculation valve and is activated via the engine cable harness.
It is particularly important for the present invention that the exhaust-gas recirculation valve is operatively connected to the cooling means or coolant flow in the engine""s cylinder head. As a result, if required as it is in the full-load operational engine mode, the exhaust gas can be cooled which also cools the recirculation valve. Consequently, the electromechanical actuator of the recirculation valve is protected from excessive temperatures.
In connection with the design and arrangement according to the invention, it is advantageous that the exhaust-gas recirculation valve and the exhaust-gas supply means are arranged on the cooler side. of the cylinder head as determined by the coolant flow through the engine.
It is advantageous, furthermore, if the exhaust gas recirculation line has a portion integrated with the cylinder head and an external portion.
It is also advantageous, if the engine exhaust gas system and the exhaust gas recirculation valve are operatively connected via an integrated exhaust-gas recirculation passage. The integrated exhaust-gas recirculation passage is designed as a part of the cylinder head. The exhaust gas line transfers heat through its wall to the cylinder head and/or to coolant in the cylinder head.
However, it is also possible for the exhaust-gas recirculation valve and exhaust-gas supply means to be operatively connected via an external exhaust-gas recirculation line. The external exhaust-gas recirculation line is preferably designed as a combination pipe including an exhaust-gas passage and a cooling-water passage. The cooling-water passage is in communication with the cooling-water circuit of the cylinder head via the exhaust-gas recirculation valve. The distance between the exhaust-gas recirculation valve and the cylinder head and the associated exhaust-gas temperature may be varied.
In a further refinement of the invention, the inflow orifice for fresh air is connected to the charge-air line, the inflow orifice for exhaust gas is connected to the external exhaust-gas recirculation line, the outflow orifice for fresh air to the charge-air distributor and the outflow orifices for exhaust gas likewise are connected to the charge-air distributor. The exhaust-gas stream is thus mixed with the fresh-air stream. After the exhaust gas flows is introduced centrally into the fresh-air stream, the process of mixing the two gas streams commences. During this time, no appreciable soot/oil deposits occur in the region of the exhaust-gas supply means, and clogging is prevented.
In connection with the arrangement according to the invention, it is advantageous that the exhaust-gas recirculation valve is provided directly upstream of the exhaust-gas supply means, as seen in the direction of flow. The exhaust-gas recirculation valve and exhaust-gas supply means are arranged functionally in one housing and being flow-connected via the inflow orifice for exhaust gas. The functional separation of exhaust-gas recirculation valve and exhaust-gas supply means ensures that the exhaust-gas recirculation valve does not have the fresh-air stream flowing around it and therefore is not cooled by the air.